Uncovering β-relaxations in amorphous phase-change materials

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  • Si Xu Peng, Huazhong University of Science and Technology
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  • Yudong Cheng, Institute of Physics (IA), RWTH Aachen University
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  • Julian Pries, Institute of Physics (IA), RWTH Aachen University
  • ,
  • Shuai Wei
  • Hai Bin Yu, Huazhong University of Science and Technology
  • ,
  • Matthias Wuttig, Institute of Physics (IA), RWTH Aachen University, JARA-Institute Green IT (PGI-10, FZ-Jülich

Relaxation processes are decisive for many physical properties of amorphous materials. For amorphous phase-change materials (PCMs) used in nonvolatile memories, relaxation processes are, however, difficult to characterize because of the lack of bulk samples. Here, instead of bulk samples, we use powder mechanical spectroscopy for powder samples to detect the prominent excess wings—a characteristic feature of β-relaxations—in a series of amorphous PCMs at temperatures below glass transitions. By contrast, β-relaxations are vanishingly small in amorphous chalcogenides of similar composition, which lack the characteristic features of PCMs. This conclusion is corroborated upon crossing the border from PCMs to non-PCMs, where β-relaxations drop substantially. Such a distinction implies that amorphous PCMs belong to a special kind of covalent glasses whose locally fast atomic motions are preserved even below the glass transitions. These findings suggest a correlation between β-relaxation and crystallization kinetics of PCMs, which have technological implications for phase-change memory functionalities.

Original languageEnglish
Article numbereaay6726
JournalScience Advances
Number of pages8
Publication statusPublished - Jan 2020
Externally publishedYes

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